The present invention relates to an improved catalytic composition and its use as an oligomerization catalyst, particularly as a dimerization or trimerization catalyst, for monoolefins. The invention more specifically concerns certain compositions obtained by contacting, in any order, at least one bivalent nickel compound with at least one hydrocarbyl aluminum halide, at least one Bronsted organic acid and at least one anhydride of a carboxylic acid.
It is already known to prepare catalysts for dimerizing or co-dimerizing monoolefins such as ethylene, propylene or n-butenes, particularly by reacting bivalent nickel carboxylates with hydrocarbyl aluminum halides. The use of these catalysts is however sometimes objectionable since, in continuous operations, the activity is often lower than in batch operations and this activity also tends to decrease in the course of time.
A first improvement has been obtained by associating a bivalent nickel compound with a hydrocarbyl aluminum halide and a compound having Bronsted acid properties, as disclosed in the published French patent application No. 2 443 877, corresponding to U.S. Pat. No. 4,283,305.